Green Plastics, also known as bioplastics, are plastics derived from renewable biomass sources e.g. starch and oil.
What are some properties of Green Plastics?
1. Bioplastics derived from fatty acids (oil) can be utilised as a fuel resource.
[Thermal Properties]
2. High conductivity increases heat dissipation - can be used in electronics
3. Easy to mold due to lower melting temperature.
How are Green Plastics made?
Bioplastics are made by converting sugar present in plants into plastic.
Example: Production of Polyactic Acid (PLA)
1. Dextrose is fermented to form lactic acid.
2. Lactic acid undergoes dehydration to form polyactic acid oligomer - water molecules have to be removed before polymerisation as formation of water molecules then prevents growing chain of lactic acid molecules from sticking together.
3. Polyactic acid oligomers undergo thermal cracking to form lactide.
4. Lactide undergoes condensation polymerisation to form polylactic acid.
Green Plastic made from Corn Starch
Bioplastic can be easily made from corn starch.
1. Add corn oil and water into a bag, seal the bag then mix the ingredients by rubbing outside bag
2. Add 2 drops of food colouring in the mixture, seal and mix again
3. Microwave on high 25 seconds with zip slightly opened.
Lesson Learnt: Oil should be added in high proportions for the resulting plastic formed to be able to stick nicely together in one piece instead of being shattered.
Result
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| My small piece of blue plastic that managed to stick together in 1 nice flat piece |
Pros
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Cons
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1. Reduces or eliminates Greenhouse Gases in production
2. Requires less or no petrochemicals
3. Biodegradable
4. Can be utilised as a fuel
5. Slow release of carbon dioxide allows sufficient time for plants to absorb it
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1. High cost
2. Use of fertilizer and pesticides on crops
3. Carbon dioxide emissions from harvesting vehicles
4. Fossil fuels typically used to power manufacturing plants 5. Producing bioplastics often requires nearly as much energy as producing conventional plastic |
Why are Green Plastics considered to be sustainable while conventional plastics are not?
In terms of the 12 principles of Green Chemistry,
Green Plastics
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Conventional Plastics
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1.
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Green Plastics are designed so that at the end of their function, they do not persist in the environment and break down into innocuous degradation products. Green plastics are biodegradable, in that they are able to degrade from the action of naturally occurring microorganisms e.g. fungi and bacteria.
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Conventional plastics are not biodegradable. Because of its complex entanglements of polymer chains, it is hard to be decomposed.
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2.
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Green Plastics make use of a renewable raw material e.g. starch and oil.
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Conventional Plastics make use of depleting resources e.g. petroleum.
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Sources:
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